AT-A-GLANCE SUMMARY OF FINDINGS

© 2015 ESS Group, Inc.

June 5, 2015 Ms. Judy Colaluca Sand Dam Reservoir Association Glocester, Rhode Island 02814 Re: Sand Dam Reservoir Aquatic Plant Survey Report ESS Project No. S442-002.01 Dear Ms. Colaluca:

ESS Group, Inc. (ESS) is pleased to present the results of the aquatic plant survey conducted at Sand

Dam Reservoir in late May. The primary purpose of the survey was to assess the current extent and

density of exotic variable-leaf milfoil (Myriophyllum heterophyllum) beds in the pond, as well as to look for

pioneer infestations of new invasive or nuisance species, if present.

AT-A-GLANCE SUMMARY OF FINDINGS

Variable-leaf milfoil was present in Sand Dam Reservoir

o Beds were patchy with locally dense clumps

o Beds were located primarily in water deeper than 6 feet

No readily apparent changes (compared to 2012) were observed in the rest of the floral or faunal

communities

Winter drawdown and hand harvesting (as needed) are recommended to control new growths of

variable-leaf milfoil fragments along shallow shorelines

Deeper growths of variable-leaf milfoil may be controlled with diver harvesting/diver assisted

suction harvesting

If SDRA determines diver harvesting of variable-leaf milfoil not to be desirable at this time,

chemical control could also be used to control growth over the short term

METHODS

ESS completed an aquatic plant survey at Sand Dam Reservoir on May 27, 2015. For consistency with

prior mapping conducted from 2009 to 2012, aquatic plant cover (expressed as a percent of bottom

occupied) and biovolume (depth of water column filled) were mapped along the same transects as

previously. Additionally, ESS walked the shoreline of Keech Pond along the dam and examined the trash

rack at its outlet to look for signs of variable-leaf milfoil fragments potentially being discharged to Sand

Dam Reservoir.

Depending on the depth and type of plant growth at each location a pole rake, throw rake, Aquascope®

view tube and/or underwater camera were used to assess the macrophyte community. A TrimbleXT

DGPS with sub-meter accuracy was used to collect position and record species composition at selected

locations, as well as plant biovolume, and plant cover. As in previous years, particular focus was given to

mapping major invasive species beds.

Ms. Judy Colaluca June 5, 2015

Page 2 © 2015 ESS Group, Inc.

RESULTS

Aquatic Plants

Cover

Aquatic plants were documented in most (179 acres) of the pond, with plant-free areas limited to small

portions of high energy, shallow shoreline (Figure 1). Many of these plant-free areas coincided with high

densities of sunfish nests on sandy or gravelly substrates.

Dense plant cover (more than 75% of the bottom covered) was observed in approximately 34 acres of the

pond (Figure 1). This is a decrease from 2012, when dense plant cover was present over approximately

85 acres. Some of this decrease may be attributable to differences in the seasonal timing of the survey

(late May in 2015 as opposed to August in 2012). However, density tends to be less affected by season

than biovolume. Furthermore, the 2012 survey was conducted several weeks after an herbicide

treatment, which would have had the effect of reducing cover. Therefore, based on this and field

observations by ESS staff, indicating only minimal plant growth in the shallow water portions of the pond,

the observed decrease in plant cover is likely to be real.

Biovolume

Plant biovolume was low to moderate over the entire pond (Figure 2). None of the pond was

characterized by high biovolume (i.e., biovolume greater than 50%). Where areas of moderate biovolume

occurred, they were primarily associated with patchy growths of variable-leaf milfoil (Figure 3).

These plant biovolumes are lower than those observed in 2012. However, biovolume is strongly affected

by seasonal factors and would be expected to increase over the summer growing season, peaking in

August or early September. Therefore, this observation should be interpreted cautiously. A follow-up

survey later in the year would be the only way to determine whether biovolume has significantly changed

since 2012.

Species Composition

Thirteen aquatic plant species were present in Sand

Dam Reservoir at the time of survey (Table A). One

macroalgal species, six emergent plant species and

small growths of filamentous green algae

(Chlorophyceae) were also found in the pond. The most

widespread native species observed was stonewort

(Nitella sp.), which was observed at 63 percent of the

mapped locations. Variable-leaf milfoil was the only

exotic invasive species documented in the pond.

Patchy growths of invasive variable-leaf milfoil were

present over approximately 5.8 acres of the pond,

mainly in waters deeper than 6 feet and away from

shore (Figure 3). This is an increase in coverage from

2012, when milfoil was confined to one bed of less than

an acre in extent. However, while robust, growth of

variable-leaf milfoil in 2015 occurred primarily as

scattered clumps rather than extensive contiguous

beds.

Plant rake showing mixed growth of native stonewort (thin stems to left) and exotic variable-leaf milfoil (long, bushy stems to

right)



Table A. Aquatic and Emergent Plant species observed at Smith and Sayles Reservoir

Scientific Name Common Name 2010 2011 2012 2015*

Aquatic Plants and Algae

Brasenia schreberi Watershield X X X

Chara sp. Muskwort (macroalgae) X

Eriocaulon aquaticum Sevenangle pipewort X X X X

Eleocharis sp. Spikerush X X X X

Elatine sp. Waterwort X X X X

Chlorophyceae Filamentous green algae X X X X

Gratiola aurea Golden hedge-hyssop X X X X

Isoetes sp. Quillwort X X X X

Myriophyllum heterophyllum Variable-leaf milfoil X X X X

Nymphoides cordata Little floating heart X X X X

Nitella sp. Stonewort (macroalgae) X X X X

Nuphar lutea variegata Yellow water lily X X X X

Nymphaea odorata White water lily X X X

Potamogeton bicupulatus Snailseed pondweed X X X

Potamogeton natans Floating pondweed X X X X

Proserpinaca palustris Mermaid weed X

Utricularia gibba Humped bladderwort X X X X

Utricularia macrorhiza Common bladderwort X X X X

Utricularia purpurea Purple bladderwort X X X

Utricularia radiata Little floating bladderwort X X X X

Key Emergent Plants

Dulichium arundinaceum Three-way sedge X X X X

Pontederia cordata Pickerelweed X X X X

Sagittaria sp. Arrowhead X X X X

Scirpus cyperinus Wool-grass X X X

Sparganium americanum Burreed X X X X

Typha latifolia Cattail X X X Note: Species in bold red text are exotic

*Survey conducted early in the season (late May). Some species may not have been detected by the survey due to

early stage of development.

Keech Pond

No fragments of variable-leaf milfoil were observed

along Keech Pond’s northern shoreline. However, ESS

did not conduct a thorough survey of Keech Pond under

this scope of work. Therefore, caution should be used in

interpreting this observation.

Fish and Wildlife

Due to the limits of the survey and the focus on aquatic

plants, the lists of fish and wildlife observed during this The Keech Pond outlet was devoid of milfoil fragments.



study are not exhaustive. They are provided here to document the presence and direct use of the pond by

readily observable species. Any unusual observations are also highlighted.

As in previous years, centrarchid (sunfish) nests were observed in many shallow areas of the pond with

sandy substrates. Additionally, bluegill (Lepomis macrochirus), largemouth bass (Micropterus dolomieu),

and yellow perch (Perca flavescens) were directly observed at multiple locations in the pond. Several

dead fish were observed at the time of survey but were observed as widely separated individuals of

different species. Therefore, the fish mortality observed was most likely the result of stress from angler

activity or localized conditions unfavorable to fish rather than a widespread water quality problem.

Canada Goose (Branta canadensis), a resident waterfowl species previously observed in moderate to

large groups at the pond, was confined to one smaller group of three individuals in 2015. Other avian

species observed to make use of Sand Dam Reservoir included Osprey (Pandion haliaetus), Mallard

(Anas platyrhynchos) and Great Blue Heron (Ardea herodias).

As in prior surveys, multiple painted turtles (Chrysemys picta) were observed basking on emergent logs

or rocks in shallow waters of the pond. Additionally, a hatchling snapping turtle (Chelydra serpentina) was

observed near the Keech Pond dam.

CONCLUSIONS AND RECOMMENDATIONS

Overall, it appears that the winter drawdown program has been highly effective in controlling the growth of

variable-leaf milfoil in shallow waters of Sand Dam Reservoir. Even coves that were previously resistant

to the impacts of drawdown (for example, those abutting Evelyn’s Way) appeared to be milfoil-free at the

time of survey. Furthermore, ESS observed no evidence of Keech Pond contributing variable-leaf milfoil

fragments to Sand Dam Reservoir. This does not necessarily indicate that Keech Pond is no longer a

source of milfoil fragments but it does suggest that it does not currently appear to be a major source.

Although overall plant cover has decreased since 2012, native aquatic plants and macroalgae are still

common throughout the pond and plant diversity remains similar to that observed during the 2009 to 2012

period. Therefore, the management program currently appears to be effective in controlling the primary

target species (variable-leaf milfoil) without resulting in excessive negative impacts to beneficial species.

A summary of key observations and recommended actions for the management of aquatic plant growth at

Sand Dam Reservoir is as follows:

Deeper growths of variable-leaf milfoil occur over approximately 5.8 acres. However, these beds

currently appear to be patchy, consisting of scattered clumps.

o Therefore, diver harvesting or diver-assisted suction harvesting (DASH) may be an

appropriate method for removing these growths. Care would need to be taken in

removing the plants to ensure the root system is adequately removed and to avoid

releasing fragments. Costs for an outside contractor to conduct diver harvesting or DASH

may vary from $1,200 to $2,500 per day. An experience crew may be able to clear

between 0.25 to 1.0 acres per day, possibly more where the infestation is more scattered

in nature. Some lake associations build and operate their own DASH vessels, which

requires significant time and material investment but may succeed at low cost over the

long term, particularly where the group is well-organized and motivated.

To implement a diver harvesting or DASH program more than 15 feet from shore or a

permitted dock (i.e., the deepwater areas where variable-leaf milfoil is currently growing),

SDRA would first need to file a Request for Preliminary Determination with RIDEM. The



fee for filing is normally $600 but SDRA would receive a 50 percent discount due to the

fact that this approach is covered in its Lake Management Plan.

o If SDRA determines diver harvesting methods are not currently desirable or cost-

effective, chemical treatment is a short-term alternative for controlling the growth of

variable-leaf milfoil in deeper waters. A contact herbicide, such as diquat dibromide,

would kill off the top growth of the milfoil and weaken the plants. However, the plants

would be expected to regrow from root crowns next season. Should SDRA decide to use

this approach, the herbicide contractor would file for a license to apply on behalf of

SDRA.

It is likely that fragments of variable-leaf milfoil will continue to root near the shoreline as the

season progresses.

o These may be controlled through hand harvesting, as long as those performing the work

are careful to remove the entire plant (including the roots) and prevent further

fragmentation.

o Future winter drawdown is also likely to provide significant control of shallow

infestations, although the degree of control will vary from winter to winter, depending on

the timing and duration of freezing weather and snow cover.

Monitoring of the boat launch area is recommended to prevent introduction of new invasive

species to Sand Dam Reservoir via watercraft, bait buckets, etc. Other invasive plant species

may not respond as well as variable-leaf milfoil to the management actions currently used by

SDRA. Therefore, it is of utmost importance to prevent the introduction of these plants.

Aquatic plants in Sand Dam Reservoir should be monitored and mapped on at least an

annual basis to help ensure that any new invasive species infestations will be found and

managed quickly. Pioneer infestations have a higher chance of being successfully controlled or

eradicated at much lower cost than infestations that are allowed to spread over many acres of the

pond. Therefore, careful monitoring should continue to be a key focus for the Sand Dam

Reservoir management program.

Please feel free to contact the undersigned at (401) 330-1204 with any questions.

Sincerely,

ESS GROUP, INC. Matt Ladewig, CLM Project Manager Attachments

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Aquatic Macrophyte CoverMay 27, 2015

Source: 1) Roads, RIGIS, 2011 2) 1-foot Contours, USDA-NRCS, 2009 3) Orthophotography, Multiple Sources, 2015

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Aquatic Macrophyte BiovolumeMay 27, 2015



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Variable-leaf Milfoil CoverMay 27, 2015



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Documents

AT-A-GLANCE SUMMARY OF FINDINGS